In order to extract energy from engine exhaust gases, turbo chargers are often used, said chargers consisting of an exhaust-gas driven turbine which drives a compressor in order to compress the intake combustion air to the engine, thus supercharging the latter. In order to recover part of the residual energy of the exhaust gases an arrangement known as a turbo compound system is sometimes placed downstream from the turbo charger. Such a turbo compound system consists of a second exhaust-gas driven turbine which mechanically transfers energy to the engine drive shaft or the like.
In order to prevent torsional vibration that occurs in the exhaust turbine from intermingling with the engine vibrations a fluid coupling is advantageously used.
In connection with turbo compound systems the use of conventional fluid couplings, wherein circulates a contained volume of liquid, has, however, been found unsuitable, on the one hand for sealing reasons and on the other on account of the considerable thermal stress that is generated in such systems.
In order to solve this problem, the use of through-flow fluid couplings has been suggested, wherein oil from the engine lubricating system is used as a combined working and cooling medium.
A disadvantage inherent in this solution is, however, that the impurities contained in the engine lubricating oil may settle on the coupling proper. These problems are considerably aggravated if the impurities settle on the inner face of the casing, thereby preventing the rotation therein of the turbine wheel. Should the coupling for this reason become stiff, a drastically increase of the working temperature in the coupling results, with consequential risks for damages to the coupling itself as well as to the transmission connected thereto.
Solutions to the problem of sedimentation of impurities are given e.g. in U.S. Pat. No. 2,510,898 describing a fluid coupling the turbine wheel of which is provided with protruding agitators arranged to increase the movability of the liquid in front of the outlet. In the subject case, this solution is, however, inadequate.